Trifluoroacetic acid → 6-methoxy-3,4-dihydro-2H-1,4-benzoxazin-3-one

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Reaction Conditions

Reaction Steps

2-bromo-N-[2-hydroxy-5-(methyloxy)phenyl]acetamide (3.42 g, 13.1 mmol), was dissolved in 120 mL of anhydrous dimethylformamide under argon. Potassium carbonate was added and suspended in the solution at room temperature. The mixture was warmed to 85° C. and refluxed for one hour before it was determined to be complete by LCMS (two Aquasil C 18, 20×1 mm columns were run in sequence, 4 minutes at 0.1 mL/min, 1-99% CH3CN/H2O with 0.018% trifluoroacetic acid, ES) Rt=1.1 min and m/e 180 [M+1]+. The mixture was allowed to cool to room temperature before it was diluted with 600 mL of ethyl acetate and washed with water (2×150 mL) and brine (2×150 mL). The organic phase was dried over Na2SO4, filtered and concentrated to give 6-(methyloxy)-2H-1,4-benzoxazin-3(4H)-one (2.08 g, 11.6 mmol, 88%) as a brown amorphous solid. MS (ES) m/e 180 [M+H]+.

Provenance & Evidence